A senior Republican familiar with the process said "a question of clarity regarding the lines of authority" was central in Harward's decision.

"I wouldn't call it a disagreement as much as questions that could not be resolved to his comfort level," the Republican said.

Ret. Army Maj. Gen. James "Spider" Marks, a CNN military analyst, called Harward an "incredibly talented guy" in an interview with CNN's Erin Burnett on "OutFront," adding that he is close to Defense Secretary James Mattis.

Marks said he didn't want to speculate why Harward turned down the job, but said turmoil in the White House was likely a contributing factor.

"I'm sure Bob looked at this, Adm. Harward looked at this, and said, 'Look there's a lot of forming and storming going on right now.'"